in short -
flash or photoshop, but i'm not a fan of later one.
In long - using flash off-camera besides catch light will also give you nicer

, less flat :meh: of lighting.
If you're asking about catchlight, it is probably that you aren't familiar with how to use camera flash, thus best advice is start learning lighting. There are hundreds of tutorials, books, videos out there. Here are few names of people that I think are pretty good to learn from: Steve Sint, David Ziser, James Schmelzer, Joe McNally, the list DOES go on and on but if you google, or you tube these names you'll get hit with lots of stuff.
Here's a site, that I feel (and it is my opinion
not a fact

) does a pretty good job explaining various portrait lighting patterns
Portrait Lighting.
Welcome to the wonderful world of lighting, you are on the way of become greater then you are right now. :thumbup:
Holla back for more input